"NEW YORK -- U.S. environmental group the Sierra Club has asked the Environmental Protection Agency's inspector general to investigate whether the agency's head, Scott Pruitt, violated internal policies when he said he did not believe carbon dioxide was a major contributor to climate change, according to a letter seen by Reuters on Wednesday.

Lawyers for the Sierra Club wrote to the EPA's Office of Inspector General on Tuesday asking the independent watchdog to check whether Pruitt violated the EPA's 2012 Scientific Integrity Policy when he told a CNBC interviewer on March 9, "I would not agree that it's a primary contributor to the global warming that we see."

The request ramps up tension between the U.S. environmental movement and the administration of President Donald Trump, who has called global warming a hoax meant to weaken the U.S. economy and has packed his Cabinet with people who question the science of climate change."

Emily Flitter reports for Reuters March 16, 2017. [2]